This invention relates to ceramic fiber compositions for use in contact with molten aluminum alloys.
Ceramic fiber refractory materials such as fiber moldable compositions and trowellable formulations of fibers and binders have many refractory applications. Lightweight and highly insulating, they find use in transfer ladle covers, patching medium for refractory superstructures, and in many aluminum metal contact applications such as liners for ladles, troughs, spouts, distribution pans, launderers and filter boxes.
Ceramic fibers are alumina-silica fibers which are either spun or blown from a melt. Although the fiber composition commonly used is about 50% Al.sub.2 O.sub.3 and 50% SiO.sub.2, fibers of higher or lower Al.sub.2 O.sub.3 levels are suitable depending upon the refractoriness required for the intended application.
Conventional fiber moldables are lightweight, highly porous materials which are not resistant to penetration and wetting by molten aluminum. In molten aluminum contact applications, a red clay parting agent is spread over the trowelled moldable to seal the surface and to retard metal penetration. However, the parting agent is also not intrinsically resistant to attack by the molten aluminum and rapid penetration of the metal into the ceramic fiber material results in a short service life.